1. Field
One embodiment of the present invention relates to a stamper for transferring patterns and, more particularly, to a stamper to be used when transferring three-dimensional patterns of the stamper onto a recording medium.
2. Description of the Related Art
Recently, as the recording density of an information recording medium increases, marks to be recorded on the medium are becoming finer. To facilitate the formation of fine recording marks, a demand has arisen for a micropatterning technique of forming three-dimensional patterns of about 100 nm or less on a recording medium. As the micropatterning technique like this, a method of combining the formation of fine patterns by lithography such as electron beam (EB) lithography or focused ion beam (FIB) lithography and the transfer of the fine patterns onto a medium substrate by nano-imprint lithography (NIL) is being studied.
On the other hand, as a medium technique for increasing the recording density, a magnetic recording system using a discrete track recording (DTR) medium having a data area and servo area is known. Three-dimensional track patterns on a recording layer of this DTR medium are formed by etching. As disclosed in, e.g., Jpn. Pat. Appln. KOKAI Publication No. 2004-110896, a stamper having three-dimensional patterns corresponding to track shapes is pressed against a resist layer to be used as an etching mask in order to transfer the patterns onto the resist layer.
Also, optical disks such as a Compact Disc (CD) and Digital Versatile Disc (DVD) are similarly required to have large capacities, and the development of multilayered-structure optical disks is advancing. A method of manufacturing the multilayered-structure optical disk is disclosed in, e.g., Jpn. Pat. Appln. KOKAI Publication No. 2003-281791. In this method, a transparent resin substrate formed from an Ni stamper by injection molding and a transparent resin stamper similarly formed by injection molding are bonded via a 2P(photopolymer) resin, and the 2P resin is cured by ultraviolet (UV) radiation. After that, patterns are transferred by separating the transparent stamper, and a multilayered-structure medium film having a thickness of a few ten μm is formed on the transferred patterns.
As the recording density of an information recording medium increases, a hard disk drive (HDD) is required to have more accurate access performance. Therefore, it is becoming more and more important to decrease the repetitive rotational error, i.e., a so-called repeatable runout (RRO) of track patterns of a recording medium. As disclosed in, e.g., Jpn. Pat. Appln. KOKAI Publication No. 2007-12258, the RRO is evaluated in an HDD after a recording medium is completed. For example, the RRO is calculated by using a positional error signal sampled when a head follows tracks on a recording medium.
Unfortunately, the RRO of the DTR medium largely depends on the characteristics of a stamper used in the process of the DTR medium. Accordingly, demands have arisen for decreasing the RRO of the stamper.